1. Field of the Invention
The present invention relates to a moving-image recording device for recording a moving image, and more specifically, to a moving-image recording device and a moving-image recording method used for a digital camera capable of recording the moving image acquired before a recording instruction.
2. Description of the Related Art
Conventionally, a technology for retro activating a time for click of a shutter even when the time for the click of the shutter has been missed, or a shutter timing has been failed in a digital camera that images and records an object by use of an image pickup element such as a CD or a CMOS sensor has been proposed by the present applicant (Jpn. Pat. Appln. KOKAI Publication No. 2000-78452).
In such a technology, a predetermined number of object images taken at even intervals are temporarily stored (cyclically stored) in a buffer such as a semiconductor memory in a recording standby state while sequentially updating them. Stated another way, a temporary storage area (buffer) of a predetermined size is provided in a memory. Object images (frame images) which are cyclically captured are sequentially stored in an empty area of the buffer. Each time when the buffer is full of data (the empty area does not remain), the oldest object image (frame image) is deleted from the buffer to keep the empty area for a new object image (frame image). Then, for example, when a shutter timing has been failed (the time for the click of the shutter has been missed), its user is prompted to perform a switching operation to a shutter timing retroaction mode. In this mode, on a monitor screen that displays a through image of the object in the recording standby state, a series of object images temporarily stored in a buffer memory are displayed sequentially in accordance with key operations, whereby the user is made to select an image at a past arbitrary recording timing desired by the user. Thereafter, the selected image is recorded as a shot image into an image recording medium such as a semiconductor memory card. To store a moving image which is captured before the shutter operation (release operation) is called a PAST capture mode.
On the other hand, most of recent digital cameras generally have not only a still image recording function but also a moving image recording function, and can record a shot moving image as video data in various video formats, including, for example, Motion JPEG (Joint Photographic coding Experts Group) format, and MPEG (Moving Picture coding Experts Group) format.
Meanwhile, in the digital camera that enables the retroaction of the time for the click of the shutter as mentioned above, the series of object images cyclically stored in the memory card may be used as a moving image. Accordingly, also in a digital camera having the moving image recording function, a predetermined number of object images taken at even intervals are temporarily and cyclically stored in the memory card, for example, in a recording standby state. As a result, at the moment of a recording and saving instruction by a shutter operation (release operation) or the like, it is possible to record a past moving image with the latest shot object image at the end.
In this case, however, a user cannot know the contents of the moving image to be recorded actually, or the accumulation condition of the object images forming the moving image, the accumulation condition including the number of effective object images (frame images) or a period of time (from the start scene to the end scene) of the object images until the user actually performs a shutter operation, etc. Therefore, it is difficult for the user to determine a timing of the shutter operation, etc. in recording a desired moving image, which has been a problem in the prior art.